Various products including food products, semiconductor products, medical products, and any other product that can have an adverse reaction to air, may be packaged in a controlled environment. Various attempts have been made to efficiently package these products in controlled environments using vacuum and/or controlled environments.
Various food products, including bakery goods, meats, fruits, vegetables, etc. are packaged under atmospheric conditions. Many of these products are presented in supermarkets, for example, in cartons or cardboard containers with a plastic or cellophane wrap covering the product.
One problem with this type of packaging is that the goods have a minimum limited shelf life, which for many products is only several days to a week. With bakery goods for example, mold may begin to grow after a few days under atmospheric conditions. Such products obviously cannot be sold or consumed and must be discarded.
Another problem arises with respect to many fruits and vegetables, which continue to ripen and continue their metabolic process under atmospheric conditions. For example, within a few days a banana can become overripe and undesirable to the consumer.
The space available for gassing operations is often limited at many facilities. In general, existing controlled environment systems are often expensive, bulky, and require three phase power, and, accordingly are impractical for use at many of these facilities.
In an effort to alleviate these problems, various attempts have been made to package food in a controlled environment by injecting controlled environment directly into filled containers. A high velocity flow is often necessary to penetrate into the food product. In general, most of these attempts have drawbacks. With bakery goods, for example, the high velocity jets can pull in air and re-contaminate the product, thereby failing to reduce the oxygen to levels that would prevent the normal onset of mold.
Various techniques for removing air in food filling processes are known in the art. Such processes are used, for example, in the packaging of nuts, coffee, powdered milk, cheese puffs, infant formula and various other dry foods. Typically, dry food containers are exposed to a controlled environment flush and/or vacuum for a period of time, subsequent to filling but prior to sealing. The product may also be flushed with a controlled environment prior to filling, or may be flushed after the filling process. When the oxygen has been substantially removed from the food contents therein, the containers are sealed, with or without vacuum. Various techniques are also known for replacing the atmosphere of packaged meat products with a modified atmosphere of carbon dioxide, oxygen and nitrogen, and/or other gases or mixtures of gases to extend shelf life.
One strategy for removing oxygen from food containers includes a conveyor belt that carries open top containers in a direction of movement directly below a gas flushing device. The gas flushing device supplies a controlled environment to the containers in two ways. First, a layer or blanket of low velocity flushing gas is supplied to the entire region immediately above and including the open tops of the containers through a distributing plate having a plurality of small openings. Second, each container is purged using a high velocity flushing gas jet supplied through a plurality of larger jet openings arranged side-by-side in a direction perpendicular to the direction of movement of the food containers. As the containers move forward, in the direction of movement, the steps of controlled environment blanketing followed by jet flushing can be repeated a number of times until sufficient oxygen has been removed from the containers and from the food contents therein.
One consideration of this strategy is that the flow of gas in a container is constantly changing. The high velocity streams are directed through perpendicular openings in a plate, which may create eddies near the openings causing turbulence which pulls in outside air. As a container moves past the perpendicular row of high velocity jets, the jets are initially directed downward into the container at the leading edge of the container's open top. As the container moves further forward, the flushing gas is directed into the center and, later, into the trailing edge of the open top, after which the container clears the row of jets before being exposed to the next perpendicular row of jets. The process is repeated as the container passes below the next row of jets.
This strategy is directed at flushing empty containers and, in effect, relies mainly on a dilution process to decrease oxygen levels. One perpendicular row of jets per container pitch may be inadequate to efficiently remove air contained in food product.
Constantly changing jet patterns in such prior art devices may create turbulence above and within the containers, which causes surrounding air to be pulled into the containers by the jets. This turbulence may also impose a limitation on the speed at which the containers pass below the jets. As the containers move faster beneath the jets, the flow patterns within the containers change faster, and the turbulence increases. Also, at high line speeds, purging gas has more difficulty going down into the containers because of the relatively shorter residence time in contact with each high velocity row. The purging gas also has a greater tendency to remain in the head space above the containers. In addition, a perpendicular arrangement of jets relative to the direction of container travel causes much of the jet to be directed outside the containers, especially when the containers are round. Moreover, the spacing apart of the perpendicular rows may further vary the flow pattern and pull outside air into the containers.
Therefore, it would be desirable to provide a strategy for exposing a container to a controlled environment that overcomes the aforementioned and other disadvantages.